This invention relates to dynamoelectric machines and more particularly to an improvement to such machines which restrains linear movement (or end play) of the rotor shaft of the machine during transport and operation. While the invention is disclosed in particular detail with respect to induction motors, those skilled in the art will recognize the wider applicability of the invention disclosed hereinafter.
One problem which may occur during transportation of an electric motor is the end rings on the rotor of the motor striking the bearing caps which are installed about the bearing assemblies which support the rotor. Violent movements, jostling, or jarring of the motor can cause the shaft to axially shift with such force that damage to either the end rings or the bearing caps may result. In either instance, the motor will need repair or replacement, and either solution is both time consuming and costly.
In the past, relatively expensive design techniques have been employed to control end play during motor operation. Generally a rotor assembly of an induction motor, for example, need not be aligned exactly with a corresponding stator assembly on start-up, as the energy of the winding will pull the rotor into alignment. However, if end play is not controlled, the rotor can strike other parts. Rotor control is desirable from at least a customer acceptance standpoint, even when lack of control does not damage the motor or inhibit proper motor operation.
The invention disclosed hereinafter provides end play control with simplified structure at low cost.